1. Field of the Invention
This invention relates to dental implements and, more particularly, to novel dental impression trays that are mechanically adjustable to accommodate various mouth sizes in order to obtain an accurate impression of an upper and/or lower dentition of a patient.
2. The Background Art
With regards to dentistry, an impression is often used to create an imprint or negative likeness of the teeth and adjacent portions of the jaw (e.g., tooth formations, the contour of the gums, etc.) preparatory to dental repair, orthodontics and restoration of missing dental structures. Impressions are typically made by placing a soft, semi-fluid material within the confines of an open trough or channel of a unitary arcuate tray which is then positioned within the mouth of a patient, thus allowing the material to set or cure. Depending upon the material used, the set impression may be either hard or have some elastic characteristics.
To provide the most accurate articulation, the impression cast should generally represent the entire dental arch. In this regard, the impression cast can be used to establish inter-proximal contacts, buccal and lingual contours and occlusion with the opposing teeth. From the negative or female cast of the teeth and surrounding structures, a positive reproduction or male cast may be created for the purpose of fabricating inlays, crowns, bridge retainers, dentures, restorations or the like.
Traditionally, before an impression cast of the dentition is created, a stock tray is selected by the dentist or dental assistant that will generally fit the dental arch of the particular patient. Since the dental arch may differ widely from patient to patient, various sizes of impression trays (e.g., small, medium, large and extra large) were developed by those skilled in the art to accommodate various mouth sizes, bite radii of teeth and to correspond to the upper and lower anterior or quadrant impression sites of patients.
For example, those skilled in the art developed prior art dental impression trays that are formed of metal, such as stainless steel, and have a pair of spaced-apart vertical walls joined by a semi-rigid mesh material disposed horizontally between the opposing vertical walls. Extending outwardly in structural relation to at least a portion of the surface facing of one of the vertical walls, a handle member may be provided to facilitate a means for gripping the impression tray for the purpose of facilitating manual manipulation of the tray. In addition, an open trough or channel may generally be formed between the opposing vertical walls, wherein the horizontally disposed mesh material provides a porous surface flooring for the trough. In preferred operation, the mesh material provides a means for permitting excess flow of impression material to become displaced and extruded there through. Dental impression trays of the prior art may further include openings formed in the vertical walls of the trough or channel which generally function as an anchoring surface for the impression, thus allowing the excess flow of impression material to become attached thereto.
Although seemingly useful for their intended purposes, there are several practical disadvantages of the prior art dental impression trays that are comprised of metal. For example, a significant disadvantage of prior art metal impression trays includes the difficulty associated with maintaining proper cleaning and sanitation of the impression trays using heat and/or chemical sterilization methods or techniques in an effort to avoid cross-contamination from one patient to another and in order to reuse these various sized, stock metal impression trays from patient to patient.
Attempting to alleviate some of the disadvantages associated with the amount of time and energy expended to maintain proper sanitation and sterilization of prior art metal impression trays, in addition to the significant costs associated therewith, disposable impression trays were developed by those skilled in the art. As noted above, since a dental arch may differ widely from patient to patient, various sizes of disposable impression trays (e.g., small, medium, large and extra large) were developed by those skilled in the art to accommodate various mouth sizes, bite radii of teeth and to correspond to the upper and lower anterior or quadrant impression sites of patients.
In accordance with other such prior art apparatus and techniques for making an impression cast of the upper and/or lower dentition of a patient, those skilled in the art developed adjustable impression trays. For example, an adjustable impression tray of the prior art may comprise a primary impression unit and a movable extension unit telescopically mounted on the primary unit for adjustment relative thereto. The primary unit may be provided with primary leg portions having secondary leg portions extending therefrom, wherein the primary leg portions include a first flap means extending outwardly therefrom and over the secondary leg portions. In operation, the secondary leg portions comprise a tab means that cooperates with the first flap means of the primary leg portions so as to facilitate the first flap means being movable relative to the tab means. The movable extension unit may further include a second flap means having a series of slots formed therein for registry with the tab means of the secondary leg portions to facilitate selective fixation in relation to the primary leg portions of the impression tray.
Another example of prior art adjustable impression trays includes a main arcuate portion with parallel spaced vertical walls having extension portions slidably disposed in frictional engagement for lengthwise adjustment in relation to the main arcuate portion. The engagement means between the extension portions and the main arcuate portion of the impression tray may include T-shaped rails formed in the outer faces of the opposing walls and corresponding recesses formed in the inner faces of the respective walls of the extension portions. Similarly, annular recesses may be formed in the outer faces of the opposing walls and corresponding annular ribs may be formed in the inner faces of the respective walls of the extension portions to provide a slidable engagement therebetween.
A meaningful disadvantage with prior art adjustable impression trays of the general type discussed herein is that they seem to only provide means for accommodating a structural adjustment in the dimensional length of the channel. In this regard, because these prior art adjustable impression trays fail to provide for any adjustment in the dimensional width of the tray to accommodate various sizes of the dental arch of patients, they are generally limited in their particular utilization.
In an effort to accommodate an adjustment in the dimensional width of a dental impression tray, those skilled in the art developed heat-expansive impression trays which may be formed of a thermoplastic material that becomes malleable at elevated temperatures so that the impression tray can be generally shaped and configured in such a manner so as to accommodate a corresponding dental arch of a particular patient. For example, prior art heat-expansive impression trays may structurally comprise an elongated channel including a buccal side, a lingual side and an occlusal side. The occlusal side of the channel including an outwardly extending folded section which may be fully or partially unfolded when the channel is heated, thereby providing a means for expanding the dimensional width of the elongated channel. Two additional folded sections formed in opposed posterior portions of the impression tray may also be provided which, when heated at a specific “softening” temperature, can be partially or fully unfolded by pulling the posterior ends of the tray away from the anterior portion of the same, thus extending the dimensional length of the elongated channel.
While prior art adjustable and heat-expansive impression trays may appear generally suitable for their intended purposes, these impression trays of the prior art nevertheless leave much to be desired from the standpoint of effectiveness of operation, manufacturing costs, simplicity of construction in relation to multiplicity of parts, and functionality as to universal application. As will be appreciated in this particular art, economic considerations are significant when dealing with the highly competitive dental industry, since multiple stock impression trays (e.g., small, medium, large and extra large) or complicated, multifaceted devices are frequently found to be commercially impractical. Accordingly, even a slight savings in cost may substantially enhance the commercial appeal of a particular component or assembly when considering issues of mass production of the product.
In accordance therewith, it would be desirable to provide an adjustable dental impression tray which realizes the advantages of the prior art devices while at the same time eliminates the disadvantages associated therewith. Such an adjustable dental impression tray is disclosed and claimed herein.